JP2020102518A - Deposition method - Google Patents

Abstract

To provide a deposition method capable of suppressing the generation of particles.SOLUTION: A deposition method for forming a thin film on the surface of a wafer 8 mounted on a boat 4 included in a low pressure CVD apparatus 1 in a reaction furnace 2 included in the low pressure CVD apparatus 1 includes a step of loading the boat 4 equipped with the wafer 8 into the reaction furnace 2 (step S2), a step of waiting until the temperature in the reaction furnace 2 loaded with the boat 4 is stabilized (step S3), and a step of evacuating the reaction furnace 2 with stable temperature (step S3).SELECTED DRAWING: Figure 1

Description

The present invention relates to a film forming method.

A method of forming a thin film on the surface of a wafer using a low pressure CVD (Chemical Vapor Deposition) device is known.
For example, in Patent Document 1, after loading a boat on which a wafer is loaded into a reaction furnace formed in a low pressure CVD apparatus, the inside of the reaction furnace is evacuated, and a source gas is supplied into the reaction furnace to supply the surface of the wafer. A method of forming a thin film is disclosed.

JP 2004-179447 A

The inventors have found the following problems regarding the film forming method.
When the boat is loaded into the reactor, the temperature inside the reactor temporarily drops and then rises. When the temperature in the reaction furnace rises, the wafer mounted on the boat thermally expands. The thermally expanded wafer may rub against the boat to generate particles.

The present invention has been made in view of such problems, and an object thereof is to provide a film forming method capable of suppressing the generation of particles.

One mode for achieving the above object is a film forming method for forming a thin film on a surface of a wafer mounted on a boat included in the low pressure CVD apparatus in a reaction furnace included in the low pressure CVD apparatus. A step of loading the loaded boat into the reactor, a step of waiting until the temperature in the reactor loaded with the boat is stable, and a step of evacuating the reactor in which the temperature is stable, Prepare

The film forming method according to the present invention comprises a step of loading a boat on which a wafer is loaded into a reaction furnace, a step of waiting until the temperature in the reaction furnace in which the boat is loaded is stabilized, and a vacuum of the reaction furnace in which the temperature is stable. And a pulling step. Since the temperature in the reaction furnace is stabilized before vacuuming, the pressure in the reaction furnace is high when the wafer thermally expands due to the temperature change in the reaction furnace. Therefore, the friction between the wafer and the boat is large, and even if the wafer thermally expands, it is possible to suppress the occurrence of friction between the wafer and the boat. Therefore, it is possible to suppress the generation of particles during evacuation.

According to the present invention, it is possible to provide a film forming method capable of suppressing the generation of particles.

It is a schematic cross section of a low pressure CVD apparatus. 6 is a flowchart showing a film forming method according to the present embodiment. 3 is a graph showing the temperature and pressure in the reaction furnace. It is a graph which shows the result of having measured the generation amount of particles.

Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. Further, the following description and the drawings are appropriately simplified to clarify the explanation.

First, the configuration of a low pressure CVD apparatus for carrying out the film forming method according to the present embodiment will be described with reference to FIG. As shown in FIG. 1, the low pressure CVD apparatus 1 includes a reaction furnace 2, a heater 3, a boat 4, a gas supply pipe 5, and an exhaust pipe 6. FIG. 1 also shows a wafer 8 in addition to the low pressure CVD apparatus 1. The reaction furnace 2 includes an outer pipe 2a and an inner pipe 2b. The arrow shown in FIG. 1 indicates the direction of gas flow.

As shown in FIG. 1, the reaction furnace 2 is a tubular structure having a ceiling. The outer tube 2a is a tubular structure extending in the vertical direction and has a ceiling. The lower end of the outer tube 2a is an open end. The inner pipe 2b is a tubular structure extending in the vertical direction, and both ends thereof are open ends. The inner pipe 2b is arranged inside the outer pipe 2a. The temperature inside the reaction furnace 2 is adjusted by using the heater 3. The position where the heater 3 is arranged is not particularly limited as long as the temperature inside the reaction furnace 2 can be adjusted. The heater 3 is arranged, for example, around the reaction furnace 2 as shown in FIG.

The boat 4 is a structure including a plate-shaped lower portion and an upper portion formed on the upper surface of the lower portion and capable of mounting the wafer 8 thereon. The boat 4 is provided with a vertical movement mechanism (not shown) and can move up and down. The wafer 8 is a thin plate member. The boat 4 may be mountable with a plurality of wafers 8 as shown in FIG. 1, or may be mountable with one wafer 8.

The upper portion of the boat 4 can enter the inside of the inner pipe 2b as shown in FIG. The boat 4 can be arranged so that the upper part of the boat 4 enters inside the inner pipe 2b and the upper surface of the lower part of the boat 4 contacts the open end of the outer pipe 2a without any gap. Therefore, when the boat 4 is arranged as shown in FIG. 1, the inside of the reaction furnace 2 can be made a closed space by the outer pipe 2a and the lower portion of the boat 4.

The gas supply pipe 5 is a pipe that connects the inner side of the inner pipe 2b and the outer side. The gas supply pipe 5 can introduce the raw material gas into the inner pipe 2b. A valve, a raw material gas tank, and the like (not shown) are connected to the outer end of the gas supply pipe 5. The raw material gas introduced using the gas supply pipe 5 is supplied into the entire reaction furnace 2 through the inside of the inner pipe 2b. The raw material gas can form a thin film on the surface of the wafer 8 mounted on the boat 4 by a chemical reaction.

Although details will be described later, in the film forming method according to the present embodiment, the inside of the reaction furnace 2 is evacuated through the exhaust pipe 6 before forming a thin film on the surface of the wafer 8. As shown in FIG. 1, the exhaust pipe 6 communicates the gap between the outer pipe 2a and the inner pipe 2b with the outside. The outer end of the exhaust pipe 6 is connected to a vacuum pump or the like (not shown). The air and raw material gas in the reaction furnace 2 are exhausted by using a vacuum pump or the like connected to the exhaust pipe 6.

Next, the film forming method according to the present embodiment will be described with reference to FIGS. FIG. 2 is a flowchart showing the film forming method according to the present embodiment. FIG. 3 is a graph showing the temperature and pressure in the reaction furnace.

As shown in FIG. 2, in the film forming method according to the present embodiment, at least a step of loading the boat 4 into the reaction furnace 2 (step S2) and a step of waiting until the temperature inside the reaction furnace 2 stabilizes ( Step S3) and a step of evacuating the reaction furnace 2 (step S4). The film forming method according to the present embodiment further includes the step of mounting the wafer 8 on the boat 4 (step S1), the step of waiting until the pressure in the reaction furnace 2 stabilizes (step S5), and the surface of the wafer 8. Each step such as the step of forming a thin film (step S6) may be provided.

In the film forming method according to the present embodiment, first, the step of mounting the wafer 8 on the boat 4 (step S1) is performed. The boat 4 is formed with a fixture for fixing the wafer 8. The fixture formed on the boat 4 has, for example, a claw shape. In step S1, the wafer 8 is fixed to the boat 4 by using the fixing tool formed on the boat 4. The number of wafers 8 mounted on the boat 4 in step S1 is not particularly limited.

Step S1 is performed in a state where the upper portion of the boat 4 has not entered the inside of the inner pipe 2b. Therefore, before carrying out step S1, the step of taking out the boat 4 from the reaction furnace 2 is usually performed. In the step of taking out the boat 4 from the reaction furnace 2, the boat 4 is lowered by using the vertical movement mechanism provided in the boat 4, and the upper portion of the boat 4 is exposed to the outside of the inner pipe 2b.

After performing the step of mounting the wafer 8 on the boat 4 (step S1), the step of loading the boat 4 on the reaction furnace 2 (step S2) is performed. In step S2, the boat 4 is raised by using the vertical movement mechanism provided in the boat 4 so that the upper portion of the boat 4 enters the inner pipe 2b. By performing step S2, the wafer 8 mounted on the boat 4 can be arranged at a predetermined position in the reaction furnace 2.

Next, a step of waiting until the temperature inside the reaction furnace 2 stabilizes (step S3) is performed. The temperature inside the reaction furnace 2 is adjusted by using the heater 3. When step S2 is performed, the temperature in the reaction furnace 2 temporarily drops, as shown in FIG. Therefore, step S3 is performed to raise the temperature in the reaction furnace 2 until it stabilizes. While performing step S3, the wafer 8 arranged in the reaction furnace 2 is affected by the temperature change in the reaction furnace 2 and thermally expands.

Next, a step of evacuating the reaction furnace 2 (step S4) is performed. In step S4, the reaction furnace 2 is evacuated using a vacuum pump or the like connected to the exhaust pipe 6. When step S4 is performed, the pressure in the reaction furnace 2 decreases as shown in FIG. When step S4 is performed, the temperature inside the reaction furnace 2 is stable, as shown in FIG.

The dotted line shown in FIG. 3 shows the pressure in the reaction furnace 2 when step S4 is performed without performing step S3. When step S3 is not performed, as shown in FIG. 3, the temperature inside the reaction furnace 2 rises in a state where the pressure inside the reaction furnace 2 is lower than when the step S3 is performed. When the pressure in the reaction furnace 2 is low, the frictional force between the wafer 8 and the boat 4 is small, so that the wafer 8 easily moves. Therefore, when the wafer 8 thermally expands, the wafer 8 and the boat 4 easily rub against each other. That is, when step S4 is performed after step S3 is performed, the wafer 8 and the boat 4 are prevented from rubbing against each other and the amount of particles generated is reduced, as compared with the case where step S4 is performed without performing step S3. be able to.

Next, a step of waiting until the pressure in the reaction furnace 2 becomes stable (step S5) is performed. Immediately after the reaction furnace 2 is evacuated, the pressure in the reaction furnace 2 is not stable, so step S5 is performed to stabilize the pressure in the reaction furnace 2. Since the temperature inside the reaction furnace 2 is stabilized in step S3, it is not necessary to wait until the temperature inside the reaction furnace 2 stabilizes after the reaction furnace 2 is evacuated in step S4.

Next, a step of forming a thin film on the surface of the wafer 8 (step S6) is performed. When performing step S6, the raw material gas is introduced into the reaction furnace 2 through the gas supply pipe 5. A thin film is formed on the surface of the wafer 8 placed in the reaction furnace 2 by a chemical reaction with the raw material gas. Through the above steps S1 to S6, it is possible to form a thin film on the surface of the wafer 8 while suppressing the particles generated during evacuation.

Hereinafter, the present invention will be specifically described with reference to examples. These descriptions do not limit the present invention.

[Example 1]
In Example 1, after loading the boat 4 on which the wafers 8 were loaded, evacuation was performed after the temperature inside the reaction furnace 2 became stable. FIG. 4 shows the results of counting the particles generated during evacuation for each lot.

[Comparative Example 1]
In Comparative Example 1, after the boat 4 carrying the wafer 8 was loaded, evacuation was started before the temperature inside the reaction furnace 2 became stable. FIG. 4 shows the result of counting particles generated during evacuation.

The results shown in FIG. 4 are summarized in Table 1 below.

As shown in Table 1, in Example 1, the average number of particles generated was 7 and the standard deviation was 4.1. In Comparative Example 1, the average number of particles generated was 22 and the standard deviation was 20. That is, in Example 1, as compared with Comparative Example 1, the amount of particles generated during evacuation was suppressed. From this, it was confirmed that the film forming method according to the present embodiment can suppress the amount of particles generated during evacuation.

The invention according to the present embodiment described above can provide a film forming method capable of suppressing the generation of particles.

The present invention is not limited to the above-mentioned embodiment, and can be modified as appropriate without departing from the spirit of the present invention.

1 low pressure CVD apparatus 2 reaction furnace 2a outer tube 2b inner tube 3 heater 4 boat 5 gas supply tube 6 exhaust tube 8 wafer

Claims (1)

A method for forming a thin film on a surface of a wafer mounted on a boat of the low pressure CVD apparatus in a reaction furnace of the low pressure CVD apparatus, comprising:
Loading the boat loaded with the wafer into the reactor;
Waiting for the temperature in the reactor loaded with the boat to stabilize,
Evacuating the reaction furnace having a stable temperature,
Deposition method.

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